The first observation of the very early stages of a supernova, only three hours after the explosion and early enough to spot the debris and determine what happened just before the destruction, is reported in a paper published online this week in Nature Physics.

Supernovae are spectacular astrophysical explosions that mark the death of massive stars. Witnessing the very early stages of a supernova can provide a glimpse into the star's environment prior to the explosion and insights into how and why stars end their lives in such a dramatic way, but such events are extremely rare.

On 6 October 2013, the Intermediate Palomar Transient Factory (iPTF), a fully automated survey of the sky, spotted an event in a nearby galaxy called NGC 7610. Shortly after the event’s discovery, different telescopes were used to observe it, and Ofer Yaron and colleagues analysed the gathered information to find out what had happened. They show that the event was a red supergiant exploding into a type II supernova. They also found evidence that the star was encircled by a disk of matter that had been created in the year before its explosion. In its final days, the star had been rapidly ejecting lots of material, losing mass before the collapse. As type II are the most common form of supernovae, the observations made by Yaron and colleagues suggest a general scenario for exploding stars.